patch 8.2.1977: Vim9: error for using a string in a condition is confusing

Problem:    Vim9: error for using a string in a condition is confusing.
Solution:   Give a more specific error.  Also adjust the compile time type
            checking for || and &&.
diff --git a/src/typval.c b/src/typval.c
index 5151f72..7c55d3a 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -196,7 +196,7 @@
 	case VAR_STRING:
 	    if (in_vim9script())
 	    {
-		emsg(_(e_using_string_as_number));
+		emsg_using_string_as(varp, !want_bool);
 		break;
 	    }
 	    if (varp->vval.v_string != NULL)